The present invention relates to a tubular carrier or dye tube for the winding up of yarns, and more particularly concerns an axially compressible or collapsible tube which can be used for the winding and dyeing of textile threads and yarns; the axially compressible tube comprises a cylindrical or frustoconical winding surface for winding up yarns, defined by a set of coaxially arranged annular or ring elements which extend parallel to each other and which are connected by flexible linking elements.
Axially compressible tubular carriers or tubes for the winding and dyeing of yarns are known for example from U.S. Pat. No. 3,465,984. These carriers are substantially composed of a plurality of parallelly arranged annular or ring elements joined by flexible connecting elements which are suitably shaped so as to facilitate the axial compression of the tube. The yarn winding-up tubes according to U.S. Pat. No. 3,465,984 have considerable applicational limitations and drawbacks because they do not ensure a sufficient degree of the dimensional stability of the tube, both in the extended condition and in the compressed condition, on account of the elastic behaviour of the transverse elements connecting the rings.
Moreover, the axial compressibility of the tube cannot be correctly controlled in any way as would otherwise be desirable in order to ensure uniform and homogeneous compression and dyeing of the wound yarn. Furthermore, uniform axial unwinding of the yarn, after compression, may be partially prevented or compromised as a result of pinching of the yarn by projecting portions of said flexible connecting elements.
U.S. Pat. Nos. 4,181,274, 4,379,529, and EP-A-348721 disclose tubes which are axially compressible in a controlled manner, there being provided axially protruding elements between adjacent rings which prevent the ring members of the tube to move closer beyond a predetermined point. Although these documents suggest the use of rigid tube structures which are able to maintain a stable shape during winding of the yarn and which then yield axially during compression, they nevertheless do not solve completely and satisfactorily the problem of providing a tube having a stable structure both in the completely extended condition and in the compressed condition of the tube while maintaining it free from deformations or projecting parts so as to preventing the pinching and to allow correct unwinding of the yarn after the dyeing process. In particular, due to recovery or the spring back movement of the plastic material from which they are moulded, said tubes do not allow a structurally stable condition to be maintained upon removal of the compressive forces; furthermore, the shape and arrangement of the flexible elements connecting the rings which make up the tube may cause deformation or rotation of the rings themselves, negatively effecting both the dyeing operation and the unwinding of the yarn from the tube in the compressed condition.
U.S. Pat. No. 4,560,116 also discloses a carrier for yarns in the form of an axially compressible tube consisting of a plurality of annular elements provided with V-shaped portions axially aligned in parallel rows and peripherally arranged in relation to the tube. The V-shaped projections of a ring are connected to corresponding V-shaped projections of adjacent rings by flexible transverse connecting elements, which are inclined relative to the longitudinal axis of the tube and whose angle of inclination is reversed when the tube is in the compressed condition. Although such a tube structure ensures a certain degree of dimensional stability in the completely extended condition, so as to withstand the radial compressive forces exerted by the yarn during winding, it does not allow any control of axial compression degree and does not ensure any dimensional stability of the tube after compression. In fact, the V-shaped configuration of the projecting parts of the rings and their axially aligned arrangement do not prevent the individual rings of the tube from deforming radially and do not allow the tube to remain in a stable compressed condition which ensures easy axial unthreading of the yarn. Moreover, owing to the absence of stop elements between the ring members, during compression of the tube the V-shaped projections could cause the pinching and breakage of the yarn and the breakage of the transverse connecting elements, thus preventing uniform unwinding of the yarn.
The object of the present invention is to provide a tubular carrier or tube for receiving textile threads and yarns, particularly for dyeing operations, which is both axially compressible and which satisfies the following requirements:
a) it must have a degree of axial compression controlled by stop elements which limit the compression of the tube to a predetermined length PA1 b) it must not cause twisting and deformation with respect to the diameter of the tube during compression, and avoid pinching or breakage of the first turns of yarn directly wound onto the tube; PA1 c) when the yarn is to be used, after dyeing, it must allow uniform unwinding and a complete unthreading of the yarn in the axial direction, so that all of the actual yarn can be used; PA1 d) it must provide a tube structure that will ensure dimensional stability both in the extended and in the compressed condition of the tube, avoiding in this latter case any spring back movement and breakage of parts of the same tube.
A further object of the invention is to provide a tubular carrier for yarns which, in addition to ensuring the advantages referred to above, has an extremely simplified design, such that it can be manufactured by moulding from plastic materials, resulting in a tube structure which is integral and free of defects or of incorrectly formed and incomplete parts.
All of the above can be achieved by means of a yarn carrier in the form of an axially compressible tubular element comprising the characteristic features of the claims.